-use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
use rustc::mir::visit::{MutVisitor, TyContext};
use rustc::mir::{BodyAndCache, Location, PlaceElem, Promoted};
use rustc::ty::subst::SubstsRef;
use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc_index::vec::IndexVec;
+use rustc_infer::infer::{InferCtxt, NLLRegionVariableOrigin};
/// Replaces all free regions appearing in the MIR with fresh
/// inference variables, returning the number of variables created.